Re: [dm-devel][PATCH] Uevent cookie env var support

From: Kay Sievers <kay sievers vrfy org>

To: device-mapper development <dm-devel redhat com>

Subject: Re: [dm-devel][PATCH] Uevent cookie env var support

Date: Wed, 8 Apr 2009 06:29:21 -0700

On Wed, Apr 8, 2009 at 05:58, Peter Rajnoha <prajnoha redhat com> wrote:
> Kay Sievers wrote:
>> If you would use the same cookie for several actions, how do you
>> track, that udev has finished the work when you expect an arbitrary
>> number of events with the same cookie?
>
> Well, I use a simple semaphore in userspace waiting for zero. So for
> every action I just increment the semaphore and when the cookie comes back
> from uevent, I decrement it (I use this cookie value as the semaphore's
> identifier as well). So the number of uevents I'm expecting is not
> arbitrary from this perspective. I just need to fire off all the actions
> and then at some point later need to be sure that all the udev rules
> were executed (so I'm sure all the nodes are created) and so I can continue.
Sure, sounds good.
I just read "we can use the cookie value to group the actions" as you
would want to use the same value for several actions.
Thanks,
Kay